Elevatable scraper drive for circular gravity thickener

ABSTRACT

The rotating underwater structure of the gravity thickener comprises two scraper arms and a central vertical cage. The cage is secured above water to a gear housing which is slidable on a rigid vertical cylindrical column. Opposite tension rods are connected to the gear reducer housing and an equalizing mechanism carried by and extending horizontally from the upper end of the column and prevent rotation of the gear reducer. The entire structure and reducer is raised and lowered hydraulically as required.

United States Patent Inventor Gilbert W. Quast Brookfield, Wis. Appl. No. 012,922 Filed Feb. 20, 1970 Patented Jan. 26, 1971 Assignee Rex Chainbelt Inc.

Milwaukee, Wis. a corporation of Wisconsin ELEVATABLE SCRAPER DRIVE FOR CIRCULAR GRAVITY THICKENER 4 Claims, 4 Drawing Figs.

US. Cl 210/531 Int. Cl BOId 21/20 Field of Search 2 1 0/5 31 [56] References Cited UNITED STATES PATENTS 2,418,973 4/1947 Hardinge 210/531 3,200,956 8/1965 Raynor et al. 210/531 3,465,888 9/1969 Fablon 210/531 Primary ExaminerJ. L. DeCesare Attorneys Ernst W. Schultz and Joseph Jochrnan, Jr.

ABSTRACT: The rotating underwater structure of the gravity thickener comprises two scraper arms and a central vertical cage. The cage is secured above water to a gear housing which is slidable on a rigid vertical cylindrical column. Opposite tension rods are connected to the gear reducer housing and an equalizing mechanism carried by and extending horizontally from the upper end of the column and prevent rotation of the gear reducer. The entire structure and reducer is raised and lowered hydraulically as required.

ELEVATABLE SCRAPER DRIVE FOR CIRCULAR GRAVITY TIIICKENER BACKGROUND OF THE INVENTION l. Field of the Invention Gravity settling tanks which are designed for maximum removal of the liquid, generally water, from the suspended solids are designated as thickeners. The settled solids are generally only periodically removed from the tank by scraping to a sump. An elevatable scraper mechanism is required in many instances so that in the event that an excessive amount of settled solids has accumulated, or because of an overload for any other reason, the mechanism may be raised and continue to function. It is desirable, however, that none of the required bearings of the mechanism be underwater, These requirements generally dictate a rotating scraper mechanism in a round tank,

2. Description of the Prior Art US. Pat. No. 2,588,l l shows a scraper mechanism which is directly connected to and driven by the gear reducer unit and is elevatable with the gear reducer unit. However, the vertical guide means securing the gear reducer housing against rotation is entirely inadequate for thickeners of the type described above.

US. Pat. No. 2,418,973 shows torque arms which might be substituted for the vertical guide means referred to. These arms are adjustable in length and would provide or allow elevation of the scraper mechanism. However, such adjustment would require that the entire structure be geometrically perfect including at such times when the structure is under load. It should be understood that the load imposed on the structure may be due to an obstruction of one arm only of the structure.

BRIEF SUMMARY OF THE INVENTION The gear reducer housing is slidable and turnable on a vertical guide cylinder having its lower end fixed to the top of the pier or inlet pipe at the center of the tank. A rectangular frame fixed to the top of the cylinder carries spaced parallel shafts having ends connected to rotate together. Tension rods connecting the housing of the gear reducer and levers fixed to said shafts secures the gear reducer housing against rotation with no interference of the vertical guidance of the housing on the column.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1. is a cross section of the gravity settling tank or thickener with the scrapers in the elevated position.

FIG. 2 is a larger perspective view of the upper end of the center column of the tank and of the surrounding cage which as shown supports the scraper arms, and the drive and elevating mechanism in their lowermost position.

FIG. 3 is of reduced scale and shows in plan the frame which is fixed to the top of the guide cylinder.

FIG. 4 shows in elevation the hydraulic lifting cylinder within the vertical guide cylinder.

DETAILED DESCRIPTION The thickening tank 11 shown in the drawings is the type which would be in the order of 100 feet in diameter and includes the circular concrete footing 12 which supports the sidewalls 13. The central concrete base 14 is provided with the sump 15 and a suitable solids withdrawal line, not shown. The floor 17 slopes downward from walls 13 to base 14. The large delivery pipe 18 beneath floor 17 is connected to base 14 and communicates with the vertical feed pipe 19 which is located at the center of the tank.

The upper end of pipe 19 is provided with inlet openings 20 for the introduction of the feed into the tank and supports the horizontal, circular plate 21 which is securely fixed thereto. The efi'luent trough 22 provided with the overflow weir 23 is carried by sidewall 13 and extends around the periphery of the tank. A suitable discharge pipe, not shown, is connected to trough 22 for withdrawal of the effluent from the tank.

The steel frameworks comprising scraper arms 25 carry the scrapers 26 which travel circularly over the floor 17 of the tank to move the settled solids toward sump 15. The means for withdrawal of the solids from sump 15 is not shown. Arms 25 are fixed to the opposite sides of the rectangular cage 27 at the lower end thereof and are supported thereby. Cage 27 surrounds but is spaced from feed pipe 19 and is wholly supported by the peripheral gear ring 28 of the gear reducer 29 which rotates the cage to move the arms and scrapers.

Reducer 29 includes a rigid, circular cast housing comprising the upper and lower plates 31a and 3117. Two drive pinions, now shown, mesh with the internal gear teeth of gear ring 28. Each of the two drive pinions is driven by an electric motor 32 and a drive train including a chain drive 33, a worm gear drive 34, and the pinion gear drive 35 which is secured directly to upper plate 31a.

The upper crossmembers 36 of cage 27 are bolted to the connector plates 37 of output gear ring 28.

In the normal operation of the thickening tank, the lower plate 31!) of thegear reducer housing rests on the plate 21 fixed to the upper end of pipe 19 so that scrapers 29 are near floor 17.

In the operation of the tank, motors 32 are run continuously to rotate cage 27 and move the solids settling on floor 17 to sump 15. However, an excessive amount of solids entering the tank with the feed might overload the mechanism. This condition can be readily sensed either as an excessive electric current being drawn by the motors or the low internal resistance of the motors, or overheating of the motors or excess bearing loads in the gear trains of the reducer.

Raising of the scraper arms is provided for by the hydraulic cylinder 41 supported within the vertical guide cylinder 42 such as shown in FIG. 4. Cylinder 41 is operable to lift the beam 43 connected by rods 44 to the upper housing plate 31a of the gear reducer. As beam 43 is raised and lowered the entire rotating mechanism is lifted and lowered.

As shown in FIG. 3, the vertical sleeve 48 extends through housing plates 31a and 31b and forms a rigid structure therewith. Sleeve 48 is dimensioned to fit cylinder 42 and provide the entire vertical guidance and lateral securement of the entire scraper mechanism. The axis of sleeve 48 is coincident with the axis of gear ring 28 and sleeve 48 is, itself, entirely free to rotate on cylinder 42.

The mechanism which secures the gear reducer against counterrotation includes the frame 51 which projects horizontally from the upper end of cylinder 42. As shown in FIG. 3, frame 51 comprises the beams 52 secured directly to the top of cylinder 42 on each side of hydraulic cylinder 41, the crossbeams 53 secured to and extending across the ends of beams 52 and the parallel beams 54 which are secured to the ends of beams 53 to form a large, rigid structure. The shafts 55 at the ends of frame 51 are journaled in the bearings 56 fixed to the respective ends of beams 54.

A lever 57 is fixed to each end of shafts 55 alongside the respective bearings 56 and the four levers extend upwardly at the four comers of frame 51. The two levers 58 extending downwardly are fixed to shafts 55 alongside the diagonally opposite bearings 56 to extend downwardly. Levers 58 and two of the four levers 57 are best fonned and joined together on shafts 55, as shown.

The corresponding upper ends of the four levers 57 at the opposite ends of each of beams 54 are connected by the two tension rods 60 and suitable bearing joints so that shafts 55 can only rotate together within limits and in the same rota tional directions. The rods 61 having universal or ball joints 62a and 62b at each end are respectively connected to the lower ends of levers 58 and the upper housing plate 31a.

In the operation of the scraper mechanism, the rotation oi cage 27 by ring 23 is at all times in the clockwise direction as viewed in FIG. 2 and the arrangement of levers 57 and 58 is such that rods 61 are coupled to prevent counterclockwise rotation of gear reducer 29 without applying any lateral forces to the gear reducer which would interfere with the movement of sleeve 48 on guide cylinder 42. For that purpose, it is essential that the respective positions of ball joints 62a and ofjoints 62b are equally and oppositely disposed with respect to the axes of guide cylinder 42 and sleeve 48.

As may be noted, the angularity of rods 61 is such that the torque applied to the cage 27 reactively tends to lift the entire drive mechanism and that as the gear reducer 29 is lifted or lowered, beam 43 and rods 44 must rotate therewith. To allow such rotation, a bearing may be provided between the beam 43 and its support, or the piston and piston rod of cylinder 41 may be allowed to rotate therein.

The equalization of the effective lengths of rods 61 is required by the precision with which the sleeve 48 fits cylinder 42. In a tank of the type and size described, cylinder 42 would typically be 2 to 3 feet in diameter in order that it would have the necessary structural rigidity and torsional resistance. Typically, sleeve 48 has a vertical height or length not much if any more than its diameter. The relatively short length of sleeve 48 is of great advantage in that the overall height of the structure which is above water is thereby minimized, having in mind also that sleeve 48 on cylinder 42 provides the entire lateral securement of cage 27 and arms 25. For that purpose, a close fit would be of no usefulness if the length of rods 61 were only adjustable as in US. Pat. No. 2,418,973. Conversely, a loose fit of sleeve 48 and cylinder 42 so that slight differences in the effective lengths of rods 61 would be of no usefulness and would require additional underwater bearings such as bearings 51 of the patent referred to. With such bearings, the gear reducer 29 would then merely need to be secured laterally respecting rods 61 and three such rods as in the patent referred to would be more or entirely practicable.

According to the present invention, both cylinder 42 and sleeve 48 are machined in a lathe to true cylindrical form and the difference in their nominal dimensions is limited only by the accuracy of such machining. Typically, the internal diameter of sleeve 48 could be held to within oneor twothousandths of an inch whereby sleeve 48 on cylinder 42 provides the entire lateral stability of cage 27 and arms 25.

The present invention may be employed in tanks also which include a bridge from one side to the center of the tank. Where some other feed supply means is provided, such as by a pipe supported by a bridge, a concrete pier may be provided instead of pipe 19 to support the gear reducer 29 and the guide cylinder 42.

I claim:

1. In a gravity settling tank having a central pier extending above the waterline of the tank, a drive mechanism disposed above said pier and having a housing and a motor-driven peripheral drive ring, said drive ring having a vertical axis of rotation, a rotatable cage having its upper end secured to said drive ring and surrounding but spaced from said pier, horizontal scraper arms secured to the lower end of said cage and extending over the floor of the tank to move settled solids to the center of the tank for removal, a vertical cylindrical column having its lower end secured to the upper end of said pier and extending upwardly through a central opening of said housing, said housing having a machined bearing sleeve defining said opening and fitting said column with a nominal tolerance whereby said housing is only tumable and vertically slidable on said column, a rigid horizontal frame fixed to the upper end of said column and having spaced parallel horizontal beams extending beyond and over said cage, parallel cross shafts journally supported at opposite ends by the corresponding ends of the respective beams, the ends of said shafts being proconnectin means at their ends and the normal rotation of said drive ring eing such that said rods are in tension, the arrangement of said upper and lower rods being such that they are in equal tension at all times and do not affect the vertical move ment or guidance of the sleeve on the column, and power actuated means to effect the elevation of the scraper arms by lifting said housing on said column, said means including a linear actuator supported centrally respecting said column and a horizontal beam supported thereby above said frame and lift rods connecting said housing and the ends of said beam, said beam and rods being turnable with the housing within the limits of rotation of the housing between the upper and lower limits of its vertical movement on said column.

2. The invention of claim 1 wherein said sleeve and column comprise machined cylinders having respectively inner and outer diameters in the order of 3 feet and the diameter of the sleeve is in the order of 0.0015 inch larger than that of the column, the ends of said lower rods connected to said downward levers being equally spaced from and oppositely disposed respecting the vertical centerline of said column and the ends connected to the housing of said drive mechanism being equally spaced and oppositely disposed respecting the axis of said sleeve. K

3. The invention of claim 1 wherein said horizontal frame comprises short parallel beams fixed at their centers to the upper end of the cylindrical column, intermediate parallel beams secured to and extending across the ends of said short beams, outer parallel beams secured to and extending across the ends of said intermediate beams, and bearings secured to the ends of said last-named beams and journally supporting said cross shafts with each one of said first-named rods extending parallel to and immediately above one said last-named beams.

4. In a gravity settling tank having a central pier extending above the waterline of thetank, a drive mechanism disposed above said pier and having a housing and a motor-driven peripheral drive ring, said drive ring having a vertical axis of rotation, a rotatable cage having its upper end secured to said drive ring and surrounding but spaced from said pier, horizontal scraper arms secured to the lower end of said cage and extending over the floor of the tank to move settled solids to the center of the tank for removal, a vertical cylindrical column having its lower end secured to the upper end of said pier and extending upwardly through a central opening of said housing, said housing fitting said column with a nominal tolerance whereby said housing is only tumable and vertically slidable on said column, a rigid horizontal frame fixed to the upper end of said column and having spaced parallel horizontal beams extending beyond and over said cage, shafts journally supported by the corresponding ends of the respective beams, said shafts being provided with upward and downward levers and upper rods pivotally connecting the corresponding upward levers, lower rods connecting said downward levers and the housing of the drive mechanism, said lower rods having universal connecting means at their ends and the normal rotation of said drive ring being such that said rods are in tension, the arrangement of said lower rods being such that they are in equal tension at all times and do not affect the vertical movement or guidance of the sleeve on the column, and power actuated means to effect the elevation of the scraper arms by lifting said housing on said column. 

1. In a gravity settling tank having a central pier extending above the waterline of the tank, a drive mechanism disposed above said pier and having a housing and a motor-driven peripheral drive ring, said drive ring having a vertical axis of rotation, A rotatable cage having its upper end secured to said drive ring and surrounding but spaced from said pier, horizontal scraper arms secured to the lower end of said cage and extending over the floor of the tank to move settled solids to the center of the tank for removal, a vertical cylindrical column having its lower end secured to the upper end of said pier and extending upwardly through a central opening of said housing, said housing having a machined bearing sleeve defining said opening and fitting said column with a nominal tolerance whereby said housing is only turnable and vertically slidable on said column, a rigid horizontal frame fixed to the upper end of said column and having spaced parallel horizontal beams extending beyond and over said cage, parallel cross shafts journally supported at opposite ends by the corresponding ends of the respective beams, the ends of said shafts being provided with upward levers and upper rods pivotally connecting the corresponding upward levers, the respectively opposite ends of said shafts being provided also with downward levers, and lower rods connecting said downward levers and the housing of the drive mechanism, said lower rods having universal connecting means at their ends and the normal rotation of said drive ring being such that said rods are in tension, the arrangement of said upper and lower rods being such that they are in equal tension at all times and do not affect the vertical movement or guidance of the sleeve on the column, and power actuated means to effect the elevation of the scraper arms by lifting said housing on said column, said means including a linear actuator supported centrally respecting said column and a horizontal beam supported thereby above said frame and lift rods connecting said housing and the ends of said beam, said beam and rods being turnable with the housing within the limits of rotation of the housing between the upper and lower limits of its vertical movement on said column.
 2. The invention of claim 1 wherein said sleeve and column comprise machined cylinders having respectively inner and outer diameters in the order of 3 feet and the diameter of the sleeve is in the order of 0.0015 inch larger than that of the column, the ends of said lower rods connected to said downward levers being equally spaced from and oppositely disposed respecting the vertical centerline of said column and the ends connected to the housing of said drive mechanism being equally spaced and oppositely disposed respecting the axis of said sleeve.
 3. The invention of claim 1 wherein said horizontal frame comprises short parallel beams fixed at their centers to the upper end of the cylindrical column, intermediate parallel beams secured to and extending across the ends of said short beams, outer parallel beams secured to and extending across the ends of said intermediate beams, and bearings secured to the ends of said last-named beams and journally supporting said cross shafts with each one of said first-named rods extending parallel to and immediately above one said last-named beams.
 4. In a gravity settling tank having a central pier extending above the waterline of the tank, a drive mechanism disposed above said pier and having a housing and a motor-driven peripheral drive ring, said drive ring having a vertical axis of rotation, a rotatable cage having its upper end secured to said drive ring and surrounding but spaced from said pier, horizontal scraper arms secured to the lower end of said cage and extending over the floor of the tank to move settled solids to the center of the tank for removal, a vertical cylindrical column having its lower end secured to the upper end of said pier and extending upwardly through a central opening of said housing, said housing fitting said column with a nominal tolerance whereby said housing is only turnable and vertically slidable on said column, a rigid horizontal frame fixed to the upper end of said column and having spaced parallel horizontal beams extending beyonD and over said cage, shafts journally supported by the corresponding ends of the respective beams, said shafts being provided with upward and downward levers and upper rods pivotally connecting the corresponding upward levers, lower rods connecting said downward levers and the housing of the drive mechanism, said lower rods having universal connecting means at their ends and the normal rotation of said drive ring being such that said rods are in tension, the arrangement of said lower rods being such that they are in equal tension at all times and do not affect the vertical movement or guidance of the sleeve on the column, and power actuated means to effect the elevation of the scraper arms by lifting said housing on said column. 